between the anticyclonic eddies of the Somali Current system and the Arabian 

 Sea are especially important owing to the summer cooling caused by wind mixing 

 and evaporation accompanied by strong solar radiation in the Arabian Sea 

 (Duing, 1978). The advection of comparatively fresh (S<35.1 °/oo) equatorial 

 water from the Bay of Bengal and the Indonesian archipelago is also imperfect- 

 ly understood. The broad patch of relatively fresh water encountered off the 

 Somali Coast during the 1979 southwest monsoon season appears to be too exten- 

 sive to be attributable solely to wind-induced coastal upwelling and the 

 attendant offshore Ekman transport. The entrainment of comparatively fresh 

 (S<35.1 °/oo) equatorial water into the southern edge of the Great Whirl is a 

 likely explanation of this large patch of low salinity water extending almost 

 300 nmi from the coast. 



Not only does the Somali Current disappear and even reverse during the 

 northeast monsoon season, but there are significant variations from one south- 

 west monsoon season to the next. Each southwest monsoon season is characterized 

 by the development of a Great Whirl or Prime Eddy between about 4°N and 12°N 

 in the Somali Basin. All oceanographic measurements known to this author 

 taken during each southwest monsoon season studied reveal divergence of the 

 northeastward-setting coastal current from the coast between 9°N and 10°N just 

 south of Ras Hafun. This area south of Ras Hafun is the scene of particularly 

 strong coastal upwelling, and it is the source region of the cold water 

 separating the warm anticyclonic Great Whirl from the smaller (about 200 nmi 

 in diameter) anticyclonic Socotra Eddy southeast of Socotra Island. Although 

 the Great Whirl and the Socotra Eddy appear to be common to all southwest 

 monsoon seasons, strong coastal upwelling also occurs at 4°N to 6°N during 

 some, but not all southwest monsoon seasons. This second area of strong 

 coastal upwelling is associated with a strong coastal current turning offshore 

 at about 5°N which forms a boundary between the Great Whirl and a southern 

 eddy centered between the equator and 4°N. During 1970 (Bruce, 1973) and 1976 

 (Bruce, 1979), the Southern Eddy formed and was separated from the Great Whirl 

 by a band of cold, coastal upwelled water originating off the Somali Coast 

 between 4°N and 6 N. During 1975, 1977, and 1978 a well developed Southern 

 Eddy was not observed (Bruce, 1979). The early part of the 1979 southwest 

 monsoon season was characterized by the formation of the Southern Eddy but 

 NOAA TIROS-N satellite infrared imagery taken 18 August and 27 August 1979 

 revealed coalescence of the Southern Eddy and the Great Whirl in only nine 

 days. 



The explanations of the variations in circulation from one southwest 

 monsoon season to the next are not clear. Bruce (1978) in tabulating mean 

 meridional and zonal wind stress values of Marsden squares 066, 067, and 031 

 for June, July, and August during each year from 1947 to 1972 found that wind 

 stress components may vary by a factor of two from year to year. It thus 

 seems reasonable to surmise some correlation between wind stress values and 

 the eddy configuration of the Somali Current System. Anderson and Rowlands 

 (1976) suggest that year to year variability in the Somali Current region may 

 be explained by slight changes in the positions and intensities of the forcing 

 functions. 



Future work in the area of the Somali Current and Arabian Sea is required 

 during all seasons in order to assess the effects of seasonally varying wind 

 stress components on the circulation in the area. Field work should involve 



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